Availability of NMR time at 600MHz is currently a limiting factor in the rate of progress of several heavily NMR-dependent NIH-funded projects at the University of Illinois at Chicago (UIC). This situation will be exacerbated by anticipated project expansion and by the recent recruitment of another NMR spectroscopist. To cost-effectively increase the available NMR instrument time on a Bruker 600MHz NMR spectrometer that is used for structural biology at UIC, it is proposed to purchase an inverse detection, triple resonance, z-gradient 5mm cryoprobe for the spectrometer. Such a cryoprobe is currently under development, and is expected to be commercially available during the funding period of this proposal. Cryoprobes have already been successfully developed at lower fields and are commercially available for 500MHz spectrometers. Based on the manufacturer's results on salt- containing aqueous samples at 500MHz, an improvement in signal-to-- noise of at least 2.4 is expected for the 600MHz cryoprobe over an equivalent probe operating with coils and preamplifier at room temperature. This would result in a saving in time for data acquisition of 5.8-fold and consequently would represent the equivalent of acquiring more than one additional 600MHz spectrometer at a fraction of the cost of such a purchase. Four research groups, that represent the primary users of the 600MHz spectrometer, will derive immediate benefit from this probe, those of Michael Caffrey, Xiubei Liao and Peter Gettins in the College of Medicine and Michael Johnson in the College of Pharmacy, in collaboration with Leslie Fung at Loyola University. All have research projects that use NMR to investigate biomedical research problems. Dr. Caffrey recently joined UIC and is working on NMR structural studies of viral proteins involved in cell infection. Dr. Liao has an established NMR-based research program examining the specificity of DNA binding by a family of "winged helix" transcription factors. Dr. Johnson and Dr. Fung are using NMR to determine the structure of the domains of spectrin, a protein that forms part of the scaffold of the red blood cell membrane. Dr. Gettins is using NMR to determine the structures of domains from proteins of the LDL receptor family and of protein ligands that bind to these receptors. Three other research groups will benefit as minor users, in collaborative projects with Dr. Gettins. These are Dr. Olson, with interests in serpin inhibition mechanism, Dr. Patston, with interests in the structure of the serpin angiotensinogen, and Dr. Silver, who is characterizing a unique silver binding protein, silE.